Allied Telesis AT-S62 - Manual (Page 495)

AT-S62 Menus Interface User’s Guide
Section IV: Spanning Tree Protocols 495
3. Adjust the MSTP settings as needed. Changes are immediately
activated on the switch. The selections are described below.
1 - Force Version
This selection determines whether the bridge operates with MSTP
or in an STP-compatible mode. If you select MSTP, the bridge
operates all ports in MSTP, except for those ports that receive STP
or RSTP BPDU packets. If you select Force STP Compatible, the
bridge uses its MSTP parameter settings, but sends only STP BPDU
packets from the ports.
2 - Hello Time
The time interval between generating and sending configuration
messages by the bridge. The range of this parameter is 1 to 10
seconds. The default is 2 seconds. This value is active only if the
bridge is selected as the root bridge of the network.
3 - Forwarding Delay
The waiting period before a bridge changes to a new state, for
example, becomes the new root bridge after the topology
changes. If the bridge transitions too soon, not all links may have
yet adapted to the change, possibly resulting in a network loop.
The range is 4 to 30 seconds. The default is 15 seconds. This
setting applies only to ports running in the STP-compatible mode.
4 - Max Age
The length of time after which stored bridge protocol data units
(BPDUs) are deleted by the bridge. This parameter applies only if
the bridged network contains an STP or RSTP single-instance
spanning tree. Otherwise, the bridges use the Max Hop counter to
delete BPDUs.
All bridges in a single-instance bridged LAN use this aging time to
test the age of stored configuration messages called bridge
protocol data units (BPDUs). For example, if you use the default of
20, all bridges delete current configuration messages after 20
seconds. The range of this parameter is 6 to 40 seconds. The
default is 20 seconds.
In selecting a value for maximum age, the following must be
observed:
MaxAge must be greater than (2 x (HelloTime + 1))
MaxAge must be less than (2 x (ForwardingDelay - 1))